1. Field of the Invention
The present invention relates to carbon fiber composite materials suitably usable for aerospace materials, and, more particularly, to carbon fiber composite materials less in mass reduction caused by atomic oxygen and excellent in endurance.
2. Related Art Statement
Recently, many artificial satellites are launched depending on their purposes, such as for communication, defense, meteorological observation, etc. and they become essential for human life. Many of these artificial satellites are launched and injected into earth orbits of low height (200-700 km from earth).
Furthermore, shuttle spacecrafts represented by the space shuttle have been steadily developed, and traffic service on a commercial base in the near future of several years from now has already been planned. As one of the representative structural materials in the field of aerospace, carbon materials such as graphite and C/C composites comprising carbon fibers and carbon powders have been widely used and they have been studied and developed.
It is known that space structures remaining in earth orbits of low height are subjected to the influence of atomic oxygen which is a main component of the atmosphere. For example, collision of atomic oxygen with the above-mentioned carbon materials causes mass reduction of the materials, resulting in deterioration of mechanical strength. This problem is serious especially in missions of long periods. On the other hand, even in the case of shuttle spacecrafts which revolve in the low height earth orbits for only a short period, it is naturally preferred to use materials which hardly undergo deterioration such as mass reduction.
The object of the present invention is to provide carbon fiber composite materials suitably usable as new aerospace materials which are much smaller in mass reduction caused by atomic oxygen and superior in endurance as compared with conventional graphite or C/C composites.
That is, the present invention provides, as the first materials, carbon fiber composite materials, characterized by being used as aerospace materials and comprising a skeletal part and a matrix integrally formed around the skeletal part, said skeletal part being mainly composed of carbon fiber bundles and silicon carbide and metallic silicon formed in the carbon fiber bundles and/or on the outer surface of the carbon fiber bundles and said matrix being mainly composed of silicon carbide and metallic silicon.
The first carbon fiber composite materials may contain a carbon component other than carbon fibers in the carbon fiber bundles. Furthermore, there may be also suitably used those which have such a composition that the content of the metallic silicon has a gradient of increasing from inside of the skeletal part toward the outer surface of the skeletal part, and/or from the outer surface of the skeletal part toward the outer surface of the matrix, and/or from the outer surface of the matrix toward inside of the matrix. Such materials can be obtained by arranging in nearly parallel with each other a plurality of yarns each of which comprises a bundle mainly composed of carbon fibers and a resin coated on the outer surface of the bundle, forming them into a sheet, laminating a plurality of the sheets in the form of multi-layer, heat-treating the laminate in a non-oxidizing atmosphere, and impregnating with metallic silicon to form integrally a skeletal part and a matrix.
Next, the present invention also provides, as the second materials, carbon fiber composite materials, characterized by being used as aerospace materials and comprising a skeletal part and a matrix integrally formed around the skeletal part with a porosity of 0.5-5% and a two-peak type distribution of average pore diameter, said skeletal part being formed of carbon fibers and a carbon component other than carbon fibers and/or silicon carbide, said matrix being formed of silicon carbide at least 50% of which is of xcex2 type.
In the second carbon fiber materials, the matrix is preferably formed along the surface of the skeletal part, and furthermore the matrix is also preferred to have such an inclined composition of the content of silicon increasing in proportion to the distance from the surface of the skeletal part. Moreover, the matrix preferably forms a continuous three-dimensional network structure.
On the other hand, the skeletal part preferably comprises a laminate obtained by two-dimensionally arranging at least a plurality of preformed yarns comprising carbon fibers and a carbon component other than carbon fibers in nearly parallel with each other thereby obtaining sheets and laminating a desired number of the sheets so that the longer directions of the preformed yarns alternately cross at right angles.
In the above-mentioned first and second carbon fiber composite materials, it is also preferred that a silicon carbide film is formed on the surface.